"We took the ACPO guidance and said 'yes, we will go with it'. And from April, when the anti-speeding campaign began, we have stuck rigidly with that policy."

Insp Bennett said camera enforcement was set at 35mph or over.

"I can assure that if anybody gets a speeding ticket through the door that says 31, 32, 33 or 34mph, then send it to me and I will have it cancelled."

Fines already paid could not be overturned as drivers will have pleaded guilty and tickets dealt with, he explained.

"But any speed camera ticket would never say less than 35mph," he said.

"If someone was to get such a ticket, it means something is wrong with the speed camera machine and we would want to know."

The road traffic chief said police officers might stop drivers at less than 35mph at their own discretion.

The driver could be charged if the officer felt the circumstances justified a fine - such as speeding outside a school.

Insp Bennett believed many drivers mistakenly felt they were caught under 35mph.

"What does happen is the driver sees the camera at the last minute, puts their brakes on and looks at the speedo, by which time the photo's taken.

"When the car went through, it was doing 35 or more."

Speed cameras are accurate to less than 1mph and always round speeds down, not up, he said.

Police forces were left with some discretion, but the guidance issued by the ACPO in February contained the following thresholds:

* In 30mph zones, a fixed penalty for speeds between 35mph and 49mph and a magistrates' summons for 50mph and above;

* In 40mph zones, a fixed penalty for speeds between 46mph and 65mph and a summons for 66mph and above;

* In 50mph zones, a fixed penalty for speeds between 57mph and 75mph and a summons for 76mph and above;

* In 60mph zones, a fixed penalty for speeds between 68mph and 85mph and a summons for speeds of 86mph and above;

* In 70mph zones, a fixed penalty for speeds between 79mph and 95mph and a summons for speeds of 96mph and above.

The ACPO said the guidance was introduced because the public expected a consistent approach from police forces across the country.

"Inconsistency in enforcement practice undermines public confidence and contributes to resentment," said a spokesman.

"It's about striking a balance between enforcing the law, without being too draconian, and keeping public confidence."

Cleveland Police's hard-line speed camera tactics have met with both harsh criticism and staunch support from scores of readers who have flooded the Gazette with calls.

Motorist Kenneth Harrow had been driving for 50 years without a blemish on his licence, before he was caught twice breaking the speeding limit in November - both times at 36mph.

The 76-year-old, of Normanby, who was fined #120 and given six penalty points on his licence, echoed the view of many callers, saying: "Police should give drivers just over the limit a warning as many drivers speed well over this speed and don't get caught."

But motorcycle instructor Dave Hammond, secretary of Cleveland Advanced Motorcyclist, hit back at complaining motorists, saying their grievances were "ridiculous".

"These people seem to be missing the point completely - the 30mph speed limit signs certainly aren't hidden and if they are caught going faster than that, then they are breaking the law," he said.

"What would these people who have been caught say if a member of their family was knocked down by a driver who was speeding?"

But Cleveland Police's use of concealed speed traps has come under fire from Teesside MPs.

Stockton South Labour MP Dari Taylor believes the force should follow Home Office advice and put mobile speed cameras in bright yellow vans, not white, to encourage motorists to cut their speed rather than trap them.

After the speeding issue was frequently raised during her constituency surgeries, the MP wrote to Home Secretary David Blunkett proposing radical changes to the system.

She said penalty points for speeding should be tapered, suggesting this should be reduced to one point for the first 5mph over the limit, two points for up to 10mph over and three points after that.

The mobile speed traps also came under fire from Stockton North MP Frank Cook who thought they were "a cock-eyed allocation of resources".

Admitting being caught speeding "on a number of occasions," the Teesside MP believes motorists will drive more slowly if they are aware of cameras rather than being caught by hidden traps.

And he suggested that if the Home Office is now recommending forces to make speed cameras more visible, then the Cleveland Constabulary should follow the guidelines.

Cleveland Police remain adamant their mobile speed cameras are playing a key role in reducing death and injury on the roads.

In the last year casualties have been reduced by 33%, with accidents down 44%, and up to 3,000 drivers are clocked every month across the area, raking in #1m a year in fines.